Since recent update my background color for text messages disappeared and I cant find how to set it the white background is annoying
You can't find it because it's not there anymore. One of the many features that One UI took away for some reason. Your only alternative is to turn off any theme that you might be running and go to Settings>Display>Night Mode and turn that on. At least it will get rid of the blinding white light.
The text message backgrounds went the way of assigning custom text message tone to the Individual and not the message thread, the Pro Video Settings, and the Pro Photo editor. Taken away from some unknown reason since Samsung won't tell us why.